Telescope Reviews: Binocular FAQs

I have been giving this matter some considerable thought over the past 24 hours.

Basically , I want to help our friend Tom with his little project , because I think a Binocular FAQ could provide a very useful , interesting and valued feature of the CN site as a whole.

The more I think about this , the more I am coming to realise that if such a feature is to exist on CN at all , it would be a discredit to the site if it were not to be as accurate, informative and interesting as possible.

When I agreed to help Tom out with this , I started out by listing the "usual suspects" such as:

Different types of binoculars
Magnification
Objective Sizes
Exit -Pupil
Eye -Relief
TFOV and AFOV
Prisms
Twighlight factor
What one can expect to see through binoculars
Hand -holdability
Aberrations
Resolution
Contrast
Advantages of "two eyes versus one eye"
Most useful configurations ( 7 x 50 v 20 x 80 etc )
"What to buy"
"Best Buys"
"Worst Buys"
"Where to buy"

etc -- etc

I soon realised that to cover even these most basic aspects by means of definition and application ,in a way that could not infringe on "copyright" whilst remaining as concise and informative as possible , at the same time as presenting something that little bit "extra" over and above what can be found at countless existing web pages , is a challenge that could probably be better taken up by a "group" effort rather than by any one individual ( especially myself ! )

As an example ,I have tonight listed a series of "questions and explanations" that I consider anyone interested in such a FAQ feature might expect to see displayed for basic educational purposes , apertaining to just ONE of the many aspects previously mentioned - i.e "PRISMS"

1. Why do binoculars have prisms ?

2. Porro prism and Roof prism Binoculars :

(a) Differences in APPEARANCE between a porro and a roof prism binocular

(b) Differences in DESIGN between a porro and a roof prism binocular

(c) Differences in PERFORMANCE between a porro and a roof prism binocular

(d) Phase Correction in roof prism binoculars

(e) Why are “giant” binoculars usually of “porro prism” type ?

(f) Potential problems and faults with prisms

(g) Different types of prism “clusters”

(h) What are the differences between Bak 4 and Bk 7 prisms ?

These are just 8 questions that sprang to my mind whilst "brainstorming" the topic -- and I know there are many members amongst us with greater brains than I have.

I COULD make an effort to explain these things myself , but I KNOW that there are others members who could do the job far better.

I am therefore most humbly appealing to any fellow -member who feels capable and so inclined to at least offer to lend a hand with this little project.

With a combined effort I feel the end result COULD be a truly invaluable source of information readily available at the touch of the fingertips and a lasting "showpiece" that would be of great credit to this wonderful site.

Regards to all -- Kenny.

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If everyone is thinking the same thing , no-one is thinking - General George S.Patton

Zeiss 7 x 42 BGAT
Captain's Helmsman 7 x 50
Nikon 10 x 42 Superior E
Swift Audubon Kestrel 10 x 50
Helios 15 x 70 Observation
Strathspey 20 x 90
Televue 76 APO
Zeiss 85 Diascope
Helios 102 f5 refractor
Various eyepieces barlows tripods mounts etc.
Panasonic Lumix DMC - TZ5 digital camera